1. Field of the Invention
The present invention relates to a product for the internal coating of a pipeline component, in particular a metal pipeline component, comprising an internal wall of high curvature.
The present invention applies more particularly to pipelines for discharge of waste water made of spheroidal graphite cast iron.
2. Description of the Related Art
Such pipelines transport particularly aggressive media which can result, in particular in hot countries, in the development in these pipelines of corrosion of bacterial origin, for example of sulphuric type or more generally of acid type.
In order to limit the effects of such corrosion, various types of internal coating for the protection of pipeline components are used. Thus, use is made, for example, of coatings obtained by curing mortars, in particular mortars based on high-alumina cement, or epoxy-based paints.
The aim of the invention is to provide a particularly effective coating which can be used industrially an economical way for the purposes of protecting from corrosion pipeline components comprising an internal wall of high curvature.
To this end, the subject-matter of the invention is a product for the internal coating of a pipeline component, in particular a metal pipeline component, comprising an internal wall of high curvature, characterized in that it comprises a solid charge and a liquid, the liquid being a solution of an alkali metal silicate and the solid charge comprising sand, between 20 and 30% by mass of a binder which sets chemically by reaction with the liquid, and between 4 and 10% by mass of plasticizing adjuvants, the solid charge and the liquid being intended to be mixed with a liquid/binder ratio by mass of between approximately 0.35 and 0.45.
According to specific embodiments, the coating product can comprise one or more of the following characteristics:
the solid charge comprises by mass, as plasticizing adjuvant, between 2 and 7% of fine silica, in particular with a particle size of less than 100 xcexcm;
the solid charge comprises by mass, as plasticizing adjuvant, between 0.4 and 0.6% of tripolyphosphate;
the solid charge also comprises, as plasticizing adjuvants, neopentyl glycol at less than 1% by mass and/or copper acetate at less than 0.5% by mass; and
the binder comprises, by mass, approximately 10% of fumed silica and 90% of fly ash and the liquid is a potassium silicate solution.
Another subject-matter of the invention is a process for the internal coating of a pipeline component, in particular a metal pipeline component, comprising an internal wall of high curvature, starting with a coating product as defined above, characterized in that:
the solid charge and the liquid of the product are mixed with a liquid/binder of the solid charge ratio by mass of approximately 0.35 to 0.45, in order to obtain a substantially homogeneous pasty mixture,
the mixture obtained is deposited in a substantially uniform way over the internal wall of the said pipeline component, and
the deposited mixture is allowed to cure, in particular by heating the pipeline component, in order to form a main internal coating.
According to specific embodiments, the process can comprise one or more of the following characteristics:
the pipeline component being substantially cylindrical with a circular base, the pipeline component is rotated about its axis in order to compact the deposit by centrifuging,
the said compacting by centrifuging is carried out after the said deposition of the mixture on the said internal wall,
the pipeline component being substantially cylindrical with a circular base, the mixture obtained is deposited on the internal wall of the pipeline component by extrusion using a nozzle and by helical relative movement of the nozzle with respect to the internal wall, in order to form a helical deposit of the mixture on the said internal wall, and
the rotational speed of the pipe during the compacting by centrifuging is much higher than the rotational speed of the pipe during the deposition of the mixture.
Another subject-matter of the invention is a pipeline component, in particular a metal pipeline component, comprising an internal wall of high curvature coated internally with an internal coating obtained by a process as defined above, characterized in that the thickness of the main internal coating is between approximately 1.5 and 15 mm.
Another subject-matter of the invention is a pipeline component comprising a pipe, in particular a metal pipe, coated internally with an intermediate coating obtained by curing a mortar, in particular a mortar based on high-alumina cement, delimiting an internal wall of high curvature, this wall being coated with a main internal coating obtained by a process as defined above, characterized in that the thickness of the main coating is between approximately 1.5 and 8 mm.
The pipeline component can be cylindrical with a circular base and its internal diameter can be between approximately 40 and 2000 mm.
A final subject-matter of the invention is a machine for depositing a pasty mixture on an internal wall of a substantially cylindrical pipeline component with a circular base, in particular for the implementation of a process as defined above, characterized in that it comprises an extrusion nozzle, exhibiting a feed orifice and a front oblong outlet opening, a mixer equipped with means for feeding with solid charge and with liquid in order to form the mixture, means for connecting the mixer to the feed orifice of the nozzle which are equipped with pumping means, means or supporting the nozzle in order to position the opening substantially parallel to the axis of the pipeline component and close to the internal wall of the pipeline component, and means for helical relative movement of the oblong opening with respect to the internal wall.
The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the appended drawings, in which: